Energy & Momentum

Question 1

Equation: Work done on an object by a constant force

Answer 1

W = F * d * cos(ø)
SI Unit = Joule = Newton * meter
Note: F = magnitude of force, d = mag of displacement, and ø = angle between force and displacement

Question 2

Only the component of the force ________ the displacement is used to define work

Answer 2

along the displacement

Question 3

In the absence of non-conservative forces (i.e. gravity), the work is independent of the _______.

Answer 3

Path taken

i.e. block lifted vertically or pushed up an inclined plane depends only on net vertical displacement

Question 4

Equation: Kinetic Energy

Answer 4

KE = 1/2 * m * v^2

SI Unit = Joule (J)

Question 5

Equation: Net Work done by ∆KE

Answer 5

W(net) = ∆KE = KE(f) - KE(o) = 1/2mv(f)^2 - 1/2mv(o)^2

Question 6

Explains the amount of energy that an object of mass m has by virtue of its position relative to the surface of the earth. Position is measured by the height (h) of the object relative to an arbitrary zero level

Answer 6

work-energy theorem

Question 7

Equation: Work-Energy Theorem

Answer 7

PE = mgh
Note: h = height above the earth
SI Unit = Joule (J)

Question 8

Equation: Gravitational Potential Energy

Answer 8

PE = mgh

Question 9

Defined as a change in the KE of a system

Answer 9

Work

SI Unit = Joule

Question 10

Equation: Conservation of Energy

Answer 10

KE(i) + PE(i) = KE(f) + PE(f)

Question 11

In the absence of forces like friction, mechanical energy is _______.

Answer 11

Conserved.

Question 12

If the kinetic energy of an object increases by a certain amount, its potential energy ________.

Answer 12

Decreases by the same amount

Question 13

the rate at which work is done

= work / time it took to perform the work

Answer 13

Power

Question 14

Equation: Power

Answer 14

Power = Work / Time = W / t

SI Unit = Joule/second = Watt (W)

Question 15

product of an object’s mass times its velocity
vector quantity that points in the same direction as velocity
conserved in the absence of an outside nonconservative force

Answer 15

momentum (p)

SI Unit = kg * m / sec

Question 16

Equation : Momentum

Answer 16

p = m * v

SI Unit = kg * m / sec

Question 17

a collision in which the total kinetic energy of the system after the collision is equal to the total kinetic energy before the collision

Answer 17

elastic collision

Question 18

Equation: Conservation of momentum

Applied to elastic collisions

Answer 18

(m1 * v1i) + (m2 * v2i) = (m1 * v1f) + (m2 * v2f)

Question 19

Collision in which the kinetic energy of the system is not conserved
collision in which the total KE of the system is not the same before and after the collision

Answer 19

inelastic collision

Question 20

collision in which objects collide and stick together

Answer 20

completely inelastic collision

Question 21

Equation: Conservation of Momentum for Completely Inelastic collisions

Answer 21

m1 * v1(i) + m2 * v2(i) = (m1 + m2) * v(f)

Question 22

In collision equations, make sure to account for the ________ of each momentum, which is a vector quantity.

Answer 22

direction

*If objects are moving toward each other, one velocity vector will be positive and one will be negative

Question 23

springs exhibit ______ behavior

Answer 23

elastic

Question 24

Equation: Hooke’s Law

Answer 24

F(restoring) = -k * x
SI Unit: N / m
Note: -k = spring constant (proportionality constant)
x = displacement of the spring from its unstrained length

Question 25

described by Hooke’s law

always points in a direction opposite to the displacement of the spring

Answer 25

restoring force

Question 26

spring constant / proportionality constant
describes stiffness of the spring
higher the value of this, the harder it is to stretch or compress the spring

Answer 26

k (-k in Hooke’s law equation)

Question 27

maximum displacement from equilibrium

Answer 27

amplitude

Question 28

for any object in simple harmonic motion, the time required to complete one cycle is called the ______

Answer 28

Period (T)

Question 29

number of cycles of motion per second
inverse of period (T)
measured in Hertz = 1 / sec

Answer 29

Frequency (f)

Question 30

Equation: Frequency

Answer 30

Frequency (f) = 1 / T

SI Unit: 1 / sec

Question 31

frequency at which object of mass m vibrates on a spring

expressed in radians per second

Answer 31

angular frequency (omega)

Question 32

Equation: Angular Frequency

Answer 32

angular frequency (omega) = 2 * π / T = 2 * π * f = √(k/m)
SI unit = Radians / second

Question 33

energy that a spring has because of being stretched or compressed

Answer 33

elastic potential energy (PE elastic)

Question 34

Equation: Elastic Potential Energy: PE (elastic)

Answer 34

PE(elastic) = 1/2 * k * x^2

SI Unit = Joule

Question 35

at max displacement from equilibrium, the PE of the spring is at a ________ and the KE is _________

Answer 35

PE = maximum
KE = 0

Question 36

total mechanical energy is conserved when nonconservative forces do no work

Answer 36

conservation of mechanical energy

Question 37

Equation: Conservation of Mechanical Energy

Answer 37

E(f) = E(i)

Question 38

Equation: Total Mechanical Energy

Answer 38

E(total) = 1/2mv^2 + mgh + 1/2kx^2

SI Unit = Joule

Question 39

Equation: Angular Freqency

Answer 39

Angular Frequency (omega) = 2πf = √(g/L)
Note: g = 10 m/s^2 and L = length (m)

Question 40

The PE of a mass at its equilibrium position =

Answer 40

0